Segment, Geographic and Revenue Information - Investment Management Asset Management Revenues - Reduction of Fees due to Fee Waivers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting [Abstract]
Fee waivers	$ 11	$ 11	$ 32	$ 45